Explosion initiating device



Jan. 29, 1957 E, KANE I 2,779,284

EXPLOSION INITIATING DEVICE Filed April 10, 1953 INVENTOR. ERNEST M. KANE ATTORNEYS United States Patent EXPLOSION INITIATING DEVICE Ernest M. Kane, Oxnard, Calif.

Application April 10, 1953, Serial No. 348,143

Claims. (Cl. 102--70) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the-payment of any royalties hereon or therefor.

The present invention relates to an explosion initiating device having a mechanical safety means and more particularly to an explosion initiating device wherein the booster or primary ignition charge is contained in a hermetically sealed chamber, and a mechanical safety means is mounted externally of the chamber.

Heretofore, explosion initiating devices have employed a mechanical safety means in the form of a valve or plug inserted in the powder train of the device to prevent detonation of the main explosive charge should the primary charge be accidentally exploded. The valve or plug is inserted in the powdertrain so as to prevent communication between the primary and main explosive charges and is therefore necessarily in frictional contact with a portion of the powder train. This type of mechanical safety means is disadvantageous since the explosive substance used as the primary charge in such devices is generally friction sensitive and therefore the dangerous possibility exists that the primary charge will be exploded when the safety means is moved from the safe to the armed position. This is obviously an undesirbale feature and presents a hazard to personnel assembling the device in firing position. Furthermore, this type of safety means must extend from the powder train to the exterior of the device, and as sufficient clearance must be provided between the safety means and the device to allow relative movement therebetween, the'gases generated by explosion of the primary charge upon firing of the device may escape through such clearance thereby reducing the efliciency of the device and possibly damaging the structure adjacent thereto at the time of firing. In devices such as rockets and gas generators where the explosion process continues for several seconds or longer, the escaping gases and the resulting fusion of structural parts may lead to complete failure of the device. The aforementioned clearance is also disadvantageous since moisture or other foreign matter may enterthe device through the clearance and come in contact with the primary charge, thereby reducing the efiiciency' of the device or possibly causing it to be inoperative.

The present invention may be utilized for initiating any type of explosion and is particularly adapted for initiating the explosion of the solid propellants of rockets, catapults and the like. The invention device provides a hermetically sealed chamber which contains the booster or primary ignition charge. The mechanical safety means is mounted externally of the chamber and may be moved from the safe to armed position independently of the chamber and without disturbing the hermetic seal thereof or contacting the explosive substance therein. In this manner, the possibility of explosion of the booster charge due to friction between the charge and the safety means is eliminated since the safety means never contacts any ice portion of the powder train of the device. In addition, the hermetically sealed chamber prevents the escape of gases generated upon explosion and also prevents moisture or other foreign matter from contacting the primary charge.

An object of the present invention is the provision of a new and novel explosion initiating device having a safety means which does not subject the primary charge of the device to friction upon relative movement of the safety means and other components of the device.

Another object is to provide an explosion initiating device which prevents the gases generated upon explosion of the primary charge from escaping from the device when it is fired.

A further object of the invention is the provision of an explosion initiating device which prevents moisture or other foreign matter from coming in contact with the primary charge of the device.

Still another object is to provide an explosion initiating device having a mechanical safety means which is simple in construction yet sturdy and reliable in operation.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 is a sectional view of a preferred embodiment of the invention,

Fig. 2 illustrates a section of the device taken on the line 2- -2 ofFig. 1 looking in the direction of the arrows,

Fig. 3 is a sectional view of a modification of the device and a Fig. 4 is a plan view of the device shown in Fig. 3.

, Referring now to the drawing, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in Fig. 1 a hollow body member or container indicated generally by reference numeral 10 which comprises a cylindrical wall portion 11 and end wall portions 12 and 13 enclosing a chamber 14. Member 10 is formed of a substance such as steel or the like having a high tensile strength. Disposed within and substantially filling chamber 14 is the primary or booster charge which is composed of black powder, flash powder or the like. mounted in wall 10 as by means of screw threads such that an air tight connection is formed between the squib and the wall portion 12. The squib extends into the interior of chamber 14 and vupon actuation is adapted to explode the booster charge. The electrical leads 'connected to the squib are hermetically sealed thereto in a manner similar to that of conventional spark plugs utilized with internal combustion engines or the like.

As may be more clearly seen in Fig. 2, two circular openings 16, 17 are formed in the cylindrical wall portion 11 at diametrically opposite points thereof, and a cen trally located circular opening 18 is formed in wall portion 13. A cylindrical diaphragm 20 is concentrically positioned about member 10 and is suitably connected at opposite ends thereof to member 10 as by brazing, welding or the like. It should be noted that the brazed portions 22, 23 extend around the entire circumference of members 10 and 20 thereby providing a hermetic seal between the body'member and the diaphragm.

Diaphragm 20 serves as a seal for openings 16 and 17 and is so designed that it will rupture at a predetermined pressure when subjected to the gases generated upon explosion of the primary charge contained in chamber 14. Member 20 is formed of a suitable ductile material such as copper, aluminum or the like which has a predictable tensilestrength, thereby enablingQthe accurate calculation An initiating squib 15 is suitably i fj acreage of the rupture point of the diaphragm. The tensile ductility of the diaphragm should be sufficient to enable it to elongate prior to rupturing.

A second diaphragm 25 formed of copper, aluminum or the like is provided for sealing opening 18 and is also adapted to rupture at a predetermined pressure in a manner similar to diaphragm 20. A retainer member 26 has screw threads 27 formed on the exterior thereof adapted to cooperate with corresponding screw threads 28 formed on member whereby member 26 is adapted to force diaphragm tightly against the lower side of wall portion 13 and thereby maintain a hermetic seal between diaphragm 25 and member 10. Member 26 has a longitudinally extending passage 29 centrally located therein, and when member 26' is in assembled position, passage 29 is aligned with opening 18. Member 26 also has screw threads 30 formed on the exterior thereof which are adapted to cooperate with corresponding screw threads formed on a member which contains a second explosive charge which may be either an intermediate ignition charge or the main explosive charge. 'It is apparent that upon rupture of diaphragm 25, member 26 will provide a path of communication between the two charges and enable the gases produced on explosion of the booster charge to detonate the second explosive charge.

Ring-like support members 31 and 32 are suitably secured as by brazing, welding or the like to the outer periphery of member 20 at opposite ends thereof. Brazed portions 33, 34 preferably extend around the entire circumference of members 31 and 32 respectively to secure the support members rigidly in place. A cylindrical safety meniber'37 is rotatably mounted 'upon diaphragm 20 and ring members 31 and 32 abut opposite ends of the safety member thereby preventing axial displacement thereof. Member 37 isformed of a material having a high tensile strength such as steel or the like and has two openings 38 and 39 formed in diametrically opposite portions thereof such that when member 37 is in the position shown in Fig. 2, openings 38 and 39 are radially aligned with openings 16 and 17, respectively. This is the safe position of the device and should the'portion of diaphragm 20 opposite either opening '16 or 17 rupture, chamber 14 would be vented to atmosphere.

Diaphragm 20 is so designed that it will rupture at a substantially lower pressure than that which will cause diaphragm 25 to rupture. Hereinafter, the diaphragm which vents the device to atmosphere will be referred to as the low pressure diaphragm and the diaphragm which vents the device to the second explosive charge will be referrerd to as the high pressure diaphragm. To provide a satisfactory margin of safety, diaphragm 20 should rupture at approximately one-tenth the pressure which is required to rupture diaphragm 25. The desired rupture point of the high and low pressure diaphragms may be obtained by varying the material or changing the thickness of the diaphragm. Furthermore, since the size of openings 38 and 39 determines the effective area of the low pressure diaphragm which is subjected to the pressure of the gases within chamber 14, the rupture point thereof may be adjusted by altering the size of openings 38 and 39.

It is evident that should the explosive substance in chamber 14 be accidentally detonated when safety member 37 is in the safe position, diaphragm 20 will rupture and vent chamber 14 to atmosphere, thereby preventing the gases in chamber 14 from reaching a sufliciently pressure to cause rupture .of member 25.

Since member 37' is rotatable with respect to the .diaphragm 20 and body member .10, the safety member-may be rotated to a position in which openings 38 and 39 are no longer in radial alignment with openings 16 and 17. When member 37 'has been rotated ninety'degrees such that openings 38 and 39 are in the phantom line position shown in Fig. '2, member 37 is in armed position and the device is ready to be fired. In this position, it is 4 evident that a solid portion of member 37 will overlie openings 16 and 17 and since member 37 is formed of a material having high tensile strength such as steel or the like, diaphragm 20 is prevented from rupturing by its inability to stretch or elongate appreciably. Therefore, the pressure within chamber 14 will increase until diaphragm 25 is ruptured, whereupon the gases will communicate with the second explosive charge which will accordingly be detonated. For maximum safety when using the device shown in Fig. 1, safety member 37 should be rotated ninety degrees in order to obtain the greatest possible misalignment of openings ,16, 17 and 38, 39 respectively. However, it may be noted that the device may be armed by rotating member 37 less than ninety degrees as long as no portion of'openings 38 and 39 overlies a portion of openings 16 01 17. Suitable detent means may be provided for maintaining the safety member in safe and armed positions.

Although the openings in the cylindrical wall portion 11 .have been shown for the purpose of illustration as two in number, any suitable number of openings may be employed according to the speed of burning of the booster charge within chamber 14. If a booster charge having a fast rate of burning is employed, a greater number of openings may be required in order to insure that diaphragm 29 will rupture before the gases within chamber 14 can build up a sufiicient pressure to rupture diaphragm 25. Furthermore, whereas the openings have been disclosed as being circular, any suitable configuration maybe utilized.

If it is desired to reduce the longitudinal dimensions of the device, a modification may be constructed as illustrated in Fig. 3, wherein the longitudinal dimensions of the cylindrical .wall portion 11 of the body member or container 10 is substantially reduced and the radial dimensions of end wall portions 12' and 13 have been increased. The booster or primary charge is disposed within enclosed chamber 14- in a manner similar to the device shown in Fig. 1. High pressure diaphragm 25 and retainer member 26 having a centrally located passage 29' are identical with members 25 and 26 employed in the device shown in Fig, 1. Squib 15' in Fig. 3 is also identical with squib 15 shown in Fig. 1, but is mounted in the cylindrical wall portion 11 rather than in an end wall portion'of the device. An opening 40 is provided in wall portion 12' and is sealed by a low pressure diaphragm 41 which is suitably secured to the body member as by brazing, welding .or the like. Member 41 is formed of a materialsimilar to that of member 20 in Fig. 1 and is designed to rupture at a predetermined pressure which is substantially less than that Which will cause rupture of member 25'. Diaphragm 41 is secured about its ,entire outer periphery to wall portion 12, thereby providing a hermetic seal between the diaphragm and the body member. A safety member 42 is slidably supported by diaphragm 41 and is guided and limited in its longitudinal movement with respect to body member lll' by a pair of tracks 43 and 44 which are rigidly secured to wall portion12' and have stopmembers 45 and 46 formed thereon.

When safety member 42 isdisposed as shown in Figs. 3 and 4, it is in safe position, and accidental detonation of the booster charge will cause diaphragm 41 to rupture. However, when member 42 is disposed as shown in the phantom lines in .Figs. 3 and 4, it is in armed position, and since member 42 overlies opening 40, diaphragm 41 will be prevented from rupturing, and the gas pressure in chamber14 twill buildup .sufiiciently to rupture diaphragm 25 and cause detonation of the second explosive charge. i

The optimum rapture pressures of the high and low diaphragms depend upon the utilization of the invention device. When it-is employed :to initiate a blasting charge or demolition charge, the low pressure diaphragms may have a.ruptureipressureinthe order of 50 p. :s. i., and the high pressure diaphragms :may accordingly have ,a rupture pressure of approximately 500. p; s. i; n the other hand, if the device is to be used to initiate a rocket or a gas genera-tor, the low pressure diaphragms must withstand the normal chamber pressure of the device, since the chamber gases will have sufficient time during the explosion process to seep through the space between the body members and the low pressure diaphragms, thereby exerting pressure on those portions of the diaphragms which are not covered by and restrained by the safety members. Therefore, the low pressure diaphragms must be designed to have rupture pressures in the order of 2000 p. s. i., and the high pressure diaphragms must accordingly have a rupture pressure of approximately 20,- 000 p. s. i. Another solution is to employ low pressure diaphragms having rupture pressures considerably less than the pressures developed by the chamber gases and to seal the diaphragms to the body members closely adjacent to the openings venting the chambers to atmosphere by means of resistance welding orthe like. In the latter case, the low pressure diaphragms will be hermetically sealed to the body members adjacent the openings therein, thereby eliminating the necessity of an additional hermetic seal.

When the primary charge consists of flash powder or a similar substance which will produce a very high temperature in chambers 14, 14 upon explosion, there is a possibility that such high temperatures will greatly lower the tensile strength of the low pressure diaphragms, causing them to rupture even when in the armed" position. To eliminate this hazard, suitable heat insulation composed of a soft, pliable substance such as zinc chromate cement, putty or the like may be disposed within openings 16, 17, 40 to protect the low pressure diaphragms from the heat developed within chambers 14, 14. Such insulation will prevent the hot gases within the chambers from appreciably lowering the rupture pressures of the low pressure diaphragms, and further-more, since the insulation is composed of a soft, pliable substance, the pressure of the gases will be transmitted substantially undimini-shed to the diaphragms.

It should be noted that in both modifications of the de' vice, the opening venting the interior of the body member to atmosphere is located nearer to the squib than the opening venting chambers 14, 14' to passages 29, 29. This is an important feature, since should squib 15 be accidentally actuated when the safety member is in the safe position, the burning gases produced by the booster charge will have an opportunity to build up pressure on the diaphragm covering the opening to atmosphere prior to building up pressure on the diaphragm covering the opening which vents the chamber to the main explosive charge, thereby insuring that diaphragms and 41 will be ruptured prior to rupture of diaphragms and 25 respectively.

From the foregoing, it is apparent that a new and novel explosion initiating device is provided in which the safety means does not subject the primary charge to friction upon relative movement of the safety means and other components of the device, since the safety means never contacts any portion of the powder train of the device. The hermetic seal between the diaphragms and the body members insures that the gases generated by explosion of the primary charge may not escape from the device, and that moisture or other foreign matter may not come in contact with the primary charge. The device is simple in construction and employs a minimum of parts, yet is sturdy and reliable in operation. 7

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What I claim:

1. An explosion initiating device which comprises a hollow body member having a closed chamber formed therein, an explosive substance disposed within .said chamber, means for selectively exploding said substance, a plurality of openings formed in said body member and communicating with said chamber, each of said openings being sealed by a diaphragm adapted to rupture when subjected to pressure, at least one of said diaphragms being adapted to rupture at a lower pressure than another of said diaphragms, and selectively operable safety means movably mounted on theexterior of said body member and being adapted to be positioned such that it overlies one of said openings and thereby prevents rupture of said one'diaphragm.

2. In an explosion initiating device, a hollow container havingan explosive substance disposed therein, means for selectively exploding said substance, a plurality of openings in said container, at least one of said openings venting the interior of said container to atmosphere, each of said openings being sealed by a pressure responsive diaphragm, at least one of said diaphragms being adapted to rupture at a lower pressure than another of said diaphragms, means for hermetically sealing said diaphragms with respect to said container, and selectively operable safety means movably mounted on the exterior of said container and being adapted to be positioned such that it overlies said one opening and thereby prevents rupture of the associated diaphragm.

3. An explosion initiating device which comprises a body member having a closed chamber formed therein, an explosive substance disposed within said chamber, a squib supported by said body member and communicating with said chamber, a first opening formed in said body member and communicating with said chamber, a first diaphragm for sealing said first opening and means for hermetically sealing said first diaphragm with respect to said body member, a second opening formed in said body member and communicating with said chamber, a sec-' ond diaphragm for sealing said second opening and a retainer means for hermetically sealing said second diaphragm with respect to said body member, said retainer means having a passage formed therein, said first diaphragm being adapted to rupture at a lower pressure than said second diaphragm, said first opening venting said chamber to atmosphere and said second opening venting Said chamber to said passage, and selectively operable safety means movably mounted on said body member and being adapted to be positioned such that it overlies said first opening and thereby prevents rupture of said first diaphragm.

4. A device as defined in claim 3 wherein each of said diaphragms is formed of a ductile metallic substance and said first opening is located intermediate said squib and said second opening.

5. An explosion initiating device which comprises a cylindrical body member closed at both ends and having a closed chamber formed therein, an explosive substance disposed within said chamber, means supported by said body member for selectively exploding said substance, a first opening formed in said body member and communicating with said chamber, a first diaphragm for sealing said first opening and means for hermetically sealing said first diaphragm with respect to said body member, a second opening formed in said body member and communicating with said chamber, a second diaphragm for sealing said second opening, a retainer means for hermetically sealing said second diaphragm with respect to said body member, said retainer means having a passage formed therein and being adapted to be secured to another member, said first opening venting said chamber to atmosphere and said second opening venting said chamber to said passage, and selectively operable safety means movably mounted on said body member and being adapted to be positioned such that it overlies said first opening and thereby prevents rupture of said first diaphragm.

6. A device as defined in claim 5 including a soft, pliable, heat insulating substance disposed in said first opening.

' 7; An explosion initiating device which comprises a cylindrical body member closed at both ends and having a'closed chamber formed therein, an explosive substance disposed within said chamber, means for selectively exploding said substance, a plurality of openings formed in said body member and communicating with'said cham bet, at least one of said openings venting said chamber to atmosphere, a diaphragm disposed in sealing relationship to each of said openings, at least one of said diaphragms being adapted to rupture at a lower pressure than an: other of said diaphragms, and a cylindrical safety member rotatably mounted on said body member and havin g an opening formed therein, said safety member being adapted tobe positioned such that said opening therein is located closely adjacent to and in radial alignment with said one opening in said body member.

8. An explosion initiating device which comprises a cylindrical body member closed at both ends and having a closed chamber formed therein, an explosive substance disposed within said chamber, means for selectively exploding said substance, a plurality of openings formed in the cylindrical portion of said body member and communicating with said chamber, a first diaphragm in sealing relation to each of said plurality of openings, means for hermetically sealing said first diaphragm with respect to said body member, another openingformed in an end portion of said body member and commnnicafl ing with said chamber, a second diaphragm is sealing relation to said other opening, retainer means for hermeticah ly sealing said second diaphragm with respect to said body member, said first diaphragm being adapted totrupture at a lower pressure than said second diaphragm, and a cylindrical safety member rotatably mountedon said body member and having a plurality of openings formed therein corresponding in number to and adapted to register with said plurality of openings in said body member, said safety member being adapted to be positioned such that said plurality of openings in said safety member are out of register with said plurality of openings in said body member thereby preventing rupture of said first diaphragm.

9. An explosion initiating device as defined in claim 5, wherein said first diaphragm is adapted to rupture at a lower pressure than said second diaphragm.

10. In an explosion initiating device, a hollow container comprising a cylindrical wall having an end wall connected to each end thereof, an explosive substance disposed within said container, means for selectively exploding said substance, at first opening formed in one end wall of said container closely adjacent said last mentioned means, a first diaphragm for hermetically sealing said first opening, a second opening formed in the opposite end wall of said container, a second diaphragm for hermetically sealing said second opening, said first diaphragm being adapted to rupture at a lower pressure than said second diaphragm, and a safety member movably mounted on said container whereby said safety member may be so positioned that it overlies that portion of said'first diaphragm which cover said first opening.

References Cited in the file of this patent UNITED, STATES PATENTS is: addition to No. 610,393, Feb. 6, 1926.)

Meister Aug. 5, 1947 

